In recent years, in general, an electric motor has been widely used as a movement control actuator of the joints of a robot. Further, to drive the robot by a sufficient power, in a robot mechanism system, various gear systems have been applied as a driving force transmission system for transmitting the driving force of the electric motor. Here, between gears, there exists a space, and consequently, there exists a backlash in the driving force transmission system using the gears. However, for example, in many robots such as a biped walking robot, the movement direction (rotational direction) of the joints reciprocally changes, and a non-linear undesirable movement occurs due to the backlash, and this is a common factor of an accurate limit of the positional (attitude) control of the joints of the robot. Particularly in the case of biped walking control of the biped walking robot, since the backlash of the joints affects the positional (attitude) control, it aggravates stability of mobile movements.
With regard to the backlash problem, in Patent Document 1, there has been proposed a technique, which is provided with a sensor for detecting a magnitude of the backlash so as to measure the backlash, and reports in case the backlash increases due to wear by aged deterioration of the gears. Further, in Patent Document 2, there has been disclosed a technique, which is provided with a zero point sensor for detecting the zero point position of movement portion of the robot, and accurately finds mechanical zero point position so as to reduce the effect of the backlash.
(Patent Document 1) Japanese Patent Laid-Open Publication No. 8-71966
(Patent Document 2) Japanese Patent Laid-Open Publication No. 10-76488
As described above, the backlash due to the gear and the like brings about instability of movement in case a highly accurate positional control is performed, and for example, in the case of the biped walking robot, there are the cases where it falls down by a slight disturbance because of unstable movement, and expected movement may not be accomplished.
In contrast to this, the technique as proposed in the Patent Document 1 is nothing more than measuring the backlash, and does not suppress the backlash small in a normal state. While the technique disclosed in the cited Document 2 attempts to detect a zero point position, and though effective for the movement control without disturbance, in case it receives an external force, for example, in case a reactive force from the floor such as thrusting a foot against the floor, raising a foot from the floor, and the like in addition to the driving force from the electric motor such as a biped walking control and the like of the biped walking robot changes, no matter how hard the zero point position is detected, there is no avoiding the occurrence of careless and irregular movements due to existence of the backlash and the external change.
Further, it is necessary to mount a sensor for measuring the backlash in the case of the Patent Document 1, and a zero point sensor in the case of the Patent Document 2, and a change of hardware is required.
An object of the present invention, in view of the circumstances, is to provide a backlash compensation control method and a backlash compensation controller which control appearance of the backlash in the movement even when a driving force transmission system has a backlash, and can perform a movement control to compensate for the backlash, and a backlash compensation control program storage medium that stores a backlash compensation control program which allows a computer to operate as such backlash compensation controller.